A digital network is comprised of a group of switches (nodes) that are connected to each other through a variety of interfaces. Asynchronous Transfer Mode (“ATM”) or “cell switching” is a technology designed for transmitting digital information such as voice, video, and data at high speeds through the digital network. The digital information is segmented into cells (fixed-length packets) and transmitted from a source node (originating node) through various intermediate nodes to a destination node. The path traversed through the network is known as a connection. Connections occasionally fail due to various causes. In a large network with many nodes, there are often multiple routes to the same destination and connection failures (and other problems) are very hard to identify and resolve.
FIG. 1 illustrates a portion of an exemplary digital network in accordance with the prior art. Network portion 100 includes a plurality of nodes A–H that are interconnected by network connections (links) 101–110. In general, the network 100 may include a variety of networks (e.g., ATM) coupling a plurality of users. A connection between users (or between particular nodes) may be established by traversing various combinations of intermediate nodes and links. For example, a connection between nodes A (e.g., source node) and node E (e.g., destination node) may be comprised of nodes B–D and links 101–105 and 111 or may be comprised of nodes F–H, and links 101 and 107–110. Additionally, nodes may be connected through multiple links as illustrated by nodes A and B, connected by links 101 and 102, and nodes D and E, connected by links 105 and 106. This increases the number of possible paths through which a connection may be established.
A particular path is dynamically selected based upon a number of different criteria so that the source node and the destination node of the connection are known, but the intermediate nodes are not known. Therefore, when a connection fails to be established, it is very difficult to determine which node generates the failure in order to effect debugging.
The network signaling protocol (e.g., Private Network to Network Interface (PNNI)) may use a number of different connection failure messages to indicate that a connection has failed. For example for a point-to-point connection a “RELEASE” or “RELEASE COMPLETE” message may be used, depending on what state the connection is in (whether a “CALL PROCEEDING” message has been sent). A “DROP-PARTY” or “ADD PARTY REJECT” message may be used for a point-to-multipoint connection.
When a connection fails (connection is released), a connection failure message is sent to the source node. The connection failure message includes a “cause code” that may explain why the connection was released. Such causes may include configuration error, software module failure, or a resource limit (e.g., node link-capacity exceeded). Many failure scenarios are possible and debugging may require a node-by-node analysis.
The ATM Forum standard “path trace” notes the path of a particular connection so that if an intermediate node releases the connection. The connection failure message then contains the path of the connection up to the failure node. Once the failure node is known, it can be examined to determine the cause of failure. The path trace is limited in that it provides only the identification of the failure node but does not provide other information needed for debugging (e.g., which software module is rejecting the connection). As such, a significant amount of debugging is still needed at the failure node to determine the cause of connection failure.